2002 bmw 325 ci keep breaking reservoir tank with

Hello, where is it breaking? It could be due to proper torque for the fasteners. Too hard to know without first hand examination. I'd definitely recommend having a shop near you have a look to see what you are experiencing. Perhaps they could offer advice with a visual inspection. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops